Create an exposed aggregate decorative concrete finish
Exposed concrete is an old technique that is very popular. Exposed aggregate finish can be widely adapted to suit your required decorative look. Your desired outcome can be created through blending our large range of colours and aggregates with the ability to produce many combinations.
What is an aggregate?
An “Aggregate” is the name given to the crushed rock and the smaller sand particles that, along with cement, make up concrete as a whole.
The finished appearance is mainly created by the choice of the aggregates.
The aggregates can vary in size from 5mm, 7mm, 10mm, and 20mm.
Different Colours Of Aggregates
The colour can vary from white quartz through to almost black basalt, there are many combinations of different colours of aggregates available.
All Types of Textures
They can vary in texture from smooth river worn pebbles that are ideal for barefoot traffic around pool areas to the sharp crushed rocks for driveways
The use of these combinations can vary on how exposed the aggregates are or for example of you choose to go for a polished finished.
GETTING THE EXPOSED EFFECT INTO THE SLAB
Seeding the aggregate onto the surface
Process by means of seeding the decorative aggregate onto the slab surface immediately after the concrete has been placed, struck off, and bull floated. This involves sprinkling the aggregate by hand or shovel uniformly onto the surface and then embedding it with a bull float until it’s completely covered by a thin layer of cement paste.
Mix the aggregate into the concrete
We put the decorative aggregate right into the concrete mix during batching, which eliminates the step of seeding it onto the surface after concrete placement depending on your desired look.
Put the aggregate into a thin topping
Another alternative is to place a thin topping course of concrete containing the decorative aggregate over a base slab of conventional concrete. The topping can range in thickness from 1 to 2 inches, depending on the aggregate size. A great method for smaller decorative aggregates are specified.
“Gives a modern look that is easy to maintain.”
How do we remove the fines? (so you know what your concretor is doing)
The simplest way for a small slab is to pour a small section of concrete and then to screed and float it so that it is flat and smooth, then wait.
Wait until the surface laitance has dried and the concrete surface is firm to the touch.
Then with a running garden hose wash the surface gently and at the same time brush the surface with a soft brush
The combination of running water and the action of the brush exposes the larger pieces of aggregate.
The whole process is one of feel / sight and experience. When to start, when to know that enough is enough.
Additives, such as retarder or accelerator, may be used to control the process of the concrete – setting quicker or held up to give more working time.
As soon as the concrete is firm enough to walk upon with smooth soled shoes, the washing out of the fines begins.
The start is made at the oldest concrete placed and working towards the last that was poured.
Use a stiff bristle broom to loosen the material and is to be washed away.
The spray pattern is used as wide as possible and the nozzle is kept well above the surface being washed, to move the sandy debris out of the way and to show quickly the progress of the work.
When this exposed aggregate work starts, a steady controlled speed is the essence.
Usually the morning after the pour the surface is again washed clean to remove any dusty film that may still be present and keeps surface moist.